The invention relates to a liquid filter comprising a housing, a cover to seal said housing, a filter element arranged within said housing, and a supporting body connected to the cover to support the filter element.
German utility model DE GM 29 602 330 discloses a liquid filter. Such liquid filters are provided with a drain, which must be sealed during filter operation. In this known fluid filter a removable filter cartridge is provided. On the drain opening, a spring-loaded sealing element is arranged, which in its closed position is held by the filter cartridge against the spring action so as to seal the drain opening. When the filter cartridge is loosened or removed, this spring-loaded sealing element unblocks the drain opening. The sealing element consists, for instance, of a plate spring, which seals the opening either directly or via a gasket.
A drawback of this arrangement is that it does not ensure a reliable seal of the drain opening by the spring-loaded sealing element. It is well known that the employed filter cartridges have a certain tolerance with respect to their diameter or their length. Due to these tolerances, the force with which the filter cartridge presses the sealing element against the drain opening varies. Under some circumstances, if the tolerances of the filter element are very large, the drain opening may not be sealed even though the filter element is installed. As a result, oil or fluid may freely flow out of the drain opening during operation, so that effective filtering of the fluid is not ensured.
The object of the invention is to obviate said drawbacks and to create a liquid filter, which seals the drain opening during normal operation irrespective of tolerances and opens it during maintenance or when the filter element is being replaced. This object is attained by the features of the independent claim.
The essential advantage of the invention is that the drain opening for the liquid is not sealed or unsealed by the filter element itself as a functional element, but by the supporting body which is arranged in the cover of the liquid filter. Said supporting body has a defined length and is actuated via the movement of the cover. This makes it possible to define a precisely adjustable sealing force.
According to one embodiment of the invention, the element, which seals or opens the drain opening is a plate spring made of spring steel, which is fixed at one end and the free end of which seals the drain opening. As mentioned above, said plate spring is actuated by the supporting body. In one embodiment of the invention, this actuation is effected by a shoulder or a bead of the supporting body.
In an alternative embodiment, the supporting body itself is provided with a spring action element, which seals or opens the drain opening. Said spring action element can be a plate spring or a tappet.
According to a further development of the invention, the filter element of the liquid filter consists of a concentrically constructed zigzag-folded filter paper, which on its end faces is provided with end disks. This filter element can be pushed onto the supporting body. To replace the filter element, the cover is opened, the supporting body unblocks the drain opening via the spring element, and the oil or fluid inside the housing can drain off. After removal of the cover, the used filter element is pulled off the support tube, and a new filter element is pushed onto it. The cover is then closed again, and the support tube simultaneously seals the drain opening via the spring element, so that new fluid to be filtered can flow in.